It is common for wells to intersect multiple zones, with each zone being subject to independent flow control via a flow control valve deployed on a tubing. In some cases, the valves used in the tubing are multi-position valves that have a number of partially open positions between fully open and fully closed.
Unfortunately, wellbores are sometimes unexpectedly shut-in (either automatically or based on a user's actions) as a result of the occurrence of certain events. If two or more valves in the wellbore are left open after the well is shut-in, then a potential for cross-flow exists between the two or more formations that correspond to the open valves. Cross-flow between formations is sometimes undesired and/or illegal.
The problem is compounded when the valves take a substantial amount of time to be activated or cycled to the fully closed position. In certain situations, time is critical in preventing any potential for cross-flow.
The problem is further compounded in injection wells. In these wells, cross-flow during shut-in can lead to the flow of solid fine particles and/or sand from one formation to another. When an operator is ready to begin injection once again, the solid fine particles that have passed between formations often minimize the injection rate into the target zone since they tend to plug the microholes associated with the target zone.